In cases where a deterministic propagation model, for example, a ray-trace algorithmic determination, is used, a conventional received electric field intensity estimating device calculates, for a number of elementary waves transmitted from a transmitter and received by a receiver, antenna gains in the receiver direction of the antenna of the transmitter (hereinafter, called “transmitter's antenna”), propagation losses, and losses resulting from reflection, diffraction and scattering caused due to the topography of the terrain and structures in the area from the transmitter to the receiver, and estimates a received electric field intensity on the basis of the result of the calculation (refer to Patent Document 1). FIG. 1 shows an example of elementary wave emanated from a transmitter and received by a receiver. According to the construction shown in FIG. 1, it is possible to carry out a received electric field intensity estimation with high accuracy.
In cases where a statistical propagation model, for example, the Okumura-Hata Formula, is used, a conventional received electric field intensity estimating device calculates antenna gains in the receiver direction of the transmitter's antenna, calculates propagation losses calculated in accordance with a propagation loss formula, and a propagation loss compensation value based on the land-use classification information (that is, information indicating an urban section, a suburban section and a forest section) for the section around the receiver, and estimates a received electric field intensity on the basis of the result of the calculation (refer to Patent Document 2). FIG. 2 shows an example of propagation loss compensation based on the land-use classification information. According to the construction shown in FIG. 2, it is possible to carry out a received electric field intensity estimation through small number of calculating processes.
However, regardless of the deterministic or statistical propagation model mentioned above, the conventional received electric field intensity estimating device carries out an averaging process or a median value calculating process on the received electric field intensity estimated in a predetermined section around the receiver so as to smooth variation in the received electric field intensity. FIG. 3 shows an example of averaging process performed on the received electric field intensity estimated in a predetermined section around a receiver.
FIG. 4 is a block diagram showing an example of the construction of a conventional received electric field intensity estimating device in the event of using a statistical propagation model, for example, the Okumura-Hata Formula.
As shown in FIG. 4, a conventional received electric field intensity estimating device includes transmitting position input unit 10, transmitting frequency input unit 11, transmitting power input unit 12, antenna's directive pattern input unit 13, receiving position input unit 14, propagation loss formula input unit 15, received electric field intensity calculation unit 16, and received electric field intensity averaging unit 17.
Hereinafter, operation of the received electric field intensity estimating device will be described with reference to FIG. 4.
First, transmitting position input unit 10, transmitting frequency input unit 11, transmitting frequency input unit 12, antenna's directive pattern input unit 13, transmitting position input unit 14, and propagation loss formula input unit 15 provide received electric field intensity calculation unit 16 with information input from external sources.
Received electric field intensity calculation unit 16 uses P[dBm] as the value of transmitting power of a signal from a transmitter, input from transmitting power input unit 12, and f[Hz] as the transmitting frequency of the signal from the transmitter, input from transmitting frequency input unit 11.
Subsequently, received electric field intensity calculation unit 16 calculates distance D[m] between a transmitting position and a receiving position and transmitting direction θo[degree] indicating the direction of a receiver viewed from the transmitter's side on the basis of the transmitting position information indicating the position of the transmitter, input from transmitting position input unit 10 and on the basis of the receiving position information indicating the position of the receiver, input from receiving position input unit 14.
Subsequently, received electric field intensity calculation unit 16 calculates gain A(θo)[dB] in transmitting direction θo[degree] of an antenna's directive pattern on the basis of the antenna's directive pattern of the transmitter's antenna input from antenna's directive pattern input unit 13.
Subsequently, received electric field intensity calculation unit 16 calculates propagation loss L=g(D,f)[dB] by using function g of propagation loss formula input from propagation loss formula input unit 15.
Subsequently, received electric field intensity calculation unit 16 calculates the propagation loss compensation value C[dB] by comparing land-use classification information for the area around the receiver input from an external source with a propagation loss compensation value table set for the land-use classification information.
Subsequently, received electric field intensity calculation unit 16 calculates received electric field intensity R[dBm] by the following equation 1, and provides received electric field intensity averaging unit 17 with the received electric field intensity R[dBm].R=P+A−(L+C)  [Equation 1]
As a final step, received electric field intensity calculation unit 16 provides received electric field intensity averaging unit 17 with the received electric field intensity R[dBm] calculated by the equation 1.
Received electric field intensity averaging unit 17 averages, on the basis of the received electric field intensity averaging section input from an external source, received electric field intensity R which is calculated for each receiver in a received electric field intensity averaging section, and outputs, as an estimated received electric field intensity, the value obtained from the averaging process to outside.